A chemical amplification resist composition containing an acid generator that generates an acid upon irradiation of an actinic ray is known as a pattern formation material in which solubility in a developing solution is differentiated between the exposed area irradiated with of an actinic ray or heat and the unexposed area to form a pattern on a substrate.
Compositions containing a mixed acid generator composed of an oxoalkylsulfonium salt and a triarylsulfonium salt or a diphenyliodinium salt are described in Patent Document 1 (JP-A-2002-116546) (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). Sulfonium salts having an oxoalkyl group are described in Patent Document 2 (JP-A-2001-187780) and Patent Document 3 (European Patent 1,113,334A). Sulfonium salts having a 2-oxocyclicalkyl group are described in Patent Document 4 (JP-A-10-133371) and Patent Document 5 (JP-A-10-73919).
Resist compositions containing a phenacylsulfonium salt having a cyclic structure are described in Patent Document 6 (JP-A-2001-294570). Resist compositions containing a mixture of an arylsulfonium salt and a phenacylsulfonium salt are described in Patent Document 7 (JP-A-2000-292917).
Chemical amplification resists containing as an acid generator, an onium salt having halogen atoms in both of a cation and an anion are described in Patent Document 8 (Japanese Patent No. 3,281,612).
Resins having an acid-decomposable group, which are used in photoresists for far ultraviolet ray, ordinarily have also an aliphatic cyclic hydrocarbon group in their molecules. The techniques described above are still insufficient in many respects and various improvements have been desired.
For instance, it has been found that in the case of using a wafer having a large diameter, fluctuation of temperature in the wafer at baking after exposure (PEB) by a hot plate or the like affects a pattern formed. Thus, it has been desired to improve such PEB dependency as well as to obtain good profile.
Patent Document 1: JP-A-2002-116546
Patent Document 2: JP-A-2001-187780
Patent Document 3: European Patent 1,113,334A
Patent Document 4: JP-A-10-133371
Patent Document 5: JP-A-10-73919
Patent Document 6: JP-A-2001-294570
Patent Document 7: JP-A-2000-292917
Patent Document 8: Japanese Patent No. 3,281,612